In many applications, where there is unequal pressure on a joint, the joint tends to bind and become less susceptible to rotation. In such applications, and in deep-sea diving suits in particular, it is desirable to have joints which can readily rotate and which are capable of flexion-extension. The problem arises because as external pressure on the joints increases, as will occur for example when a diving suit is submerged to greater depths, such joints tend to experience severely increased friction. A number of joints addressing this problem have been disclosed or provided in the past. Longitudinally flexible joints have been described which utilize a fluid-filled chamber in an attempt to minimize such incretion. For example, U.S. Pat. No. 3,759,550 to Peress discloses a flexible joint having an annular, partially spherical, male member movably housed within an annular, partially spherically shaped female member. The chamber formed between the male and female members is filled with a suitable fluid. Sealing means are provided on the female member wall. Although such a configuration helps to reduce the effect of increased external pressure, such configuration suffers from several disadvantages. One is that with the piston-cylinder arrangement, the walls of the cylinder tend to distort due to high end loads and hence the walls tend to move away from the piston. This causes loss of seal, loss or oil and subsequent jamming In other words, over a period of use, a small amount of liquid from the chamber is lost, the male and female members thereby become misaligned, and both members jam when one attempts to flex the joint. Moreover, with this joint, great care must be taken to ensure that there are no small air bubbles remaining within the fluid. in the chamber. At high external pressures, the air tends to compress thereby resulting in a decrease in the volume of the chamber, with consequent misalignment of the male and female members and seizure of the joint.
Such a result can also follow where a fluid containing joint is subjected to a very high external pressure, since even liquids are compressible to some degree under high pressures. In such cases, the seals on the female member must be forced hard against the male member to prevent oil leakage into the hollow tubes connected by the joint. Such a high force is itself a source of rotational friction.
U.S. Pat. No. 3,057,646, Brumagim, describes a cooled rotary seal between a fixed pipe and a rotating pipe of a rotary kiln. The ends of the pipes are separated and a rotary seal is maintained between stator rings of bronze or carbon located around the end of the fixed pipe and rotor rings constructed of a hard material such as tungsten carbide or ceramic. These are slidable in an annular flange around the end of the rotating pipe, and are spring-urged towards the stator rings. A liquid coolant can be introduced.
Other joints have been described in the past, which utilize a fluid-filled chamber between the two sections. Such joints are disclosed, for example, in U.S. Pat. No. 2,557,140 to Razdowitz, U.S. Pat. No. 3,754,779 to Paris, U.S. Pat. No. 1,888,026 to Chapman, and U.S. Pat. No. 4,549,753 to Nuytten. Such joints, however, tend to suffer from one or more of the above difficulties or from relative complexity of or from leakage when exposed to high external pressures.
The applicant is aware of other joint constructions which are more or less pertinent to this invention. These are listed below.
______________________________________ U.S. Pat. No. Inventor ______________________________________ 1,146,781 Bowdoin 1,888,026 Chapman 1,947,657 Peress 2,279,969 Casperson 2,421,691 Gibson, Jr. et al. 2,557,140 Razdowitz 2,726,104 Boitnott et al. 3,329,967 Martinez 3,466,061 Fonda-Bonardi 3,473,832 Kriedel, Sr. et al. 3,754,779 Peress 3,759,550 Peress 3,776,578 Jessup et al. 3,826,396 Frassica 3,889,985 Garmann 3,913,951 LeFebvre, Jr. 4,101,148 Lee 4,156,530 Rivkin et al. ______________________________________